In general, rotary unions and fluid delivery systems are well known, especially in the semiconductor processing industry. In the semiconductor processing industry, a rotary union is commonly used to facilitate the transfer of process liquid(s) from a first environment to a second environment that rotates relative to the first environment. Most commonly, one or more liquid(s) from a generally stationary supply line are being transferred to a rotating point of use. Exemplary semiconductor process tools that use one or more rotary union(s) include spray process tool systems commercially available from FSI International, Inc. and sold under the trade designations ZETA® and MERCURY®.
Rotary unions may include at least two components that rotate relative to one another. At least one component is fluidly coupled to a first environment and the at least other component is fluidly coupled to a second environment. Fluid(s), typically liquid(s), can be transferred from one environment to the other. One embodiment of a conventional rotary union is disclosed in U.S. Pat. No. 4,848,400 (Grant et al.). Another embodiment of a conventional rotary union is disclosed in U.S. Pat. No. 5,570,908 (Merritt).
Conventional components that rotate relative to one another typically have tolerances among them, and maintaining such tolerances is important. For example, if a tolerance between components widens to a point beyond that intended, leaks can occur and/or components can become too loose and/or become damaged. As another example, if a tolerance between components narrows to a point beyond that intended, the components can rub and wear and/or even prevent rotation of the rotating component(s). Thus, for a rotary union to work well, one or more appropriate tolerances among parts is established when the rotary union is manufactured and then reasonably maintained during use.
One drawback of some rotary unions is that their operation is limited to relatively narrow temperature ranges. For example, the fit among parts in a rotary union can either widen and/or narrow too much as the temperature changes (e.g., as the temperature becomes too hot and/or too cold). However, since many industrial processes that use rotary unions operate in a relatively broad temperature range, it may be desirable to use a rotary union that can perform well in such a relatively more broad temperature range. For example, many processes in the semiconductor industry treat semiconductor wafers with various process liquids that are at much different temperatures (hot and cold).
Another drawback of some rotary unions is that debris may be generated in some applications (e.g., in the manufacture of microelectronics and/or medical devices) during even normal operations of the rotary union. Such debris can be generated from several sources. It can be generated from certain components intentionally and/or unintentionally rubbing against one another. Debris can also be generated from certain components such as lubricated/greased bearings. Such debris can be undesirable because it can contaminate process fluids, which in turn can contaminate manufactured goods that have stringent product specifications (e.g., microelectronic devices and medical devices). Such debris can also be undesirable because it can cause undue wear to rotary union components and/or downstream components. For debris-sensitive applications and/or downstream components, debris generation is more unsatisfactory when debris enters a primary fluid pathway, but is less objectionable if it enters only one or more drain pathways and/or is outside the primary fluid and/or drain fluid pathway(s). Moreover, the tendency of debris to enter a primary fluid pathway can be significantly influenced by the positioning of debris-generating component(s) relative to the primary fluid and pathway.
There is a continuing need to develop rotary unions and fluid delivery systems that are new, including rotary unions that are more robust to changes in temperature and/or that present less of a risk for unsatisfactory debris generation and/or that present less of risk that any generated debris will enter a primary fluid pathway.